Electrophonic filter



1 Feb; 5, I935.

s. MABBOUX 1,990,044

mcmnornomc' FILTER Filed Nov. 18. 1931 2 Sheets-Sheet 1 Iwvewfor: Geo/yes Mafioux Feb. 5,1935. ca. MABBOUX 1,990,044

ELECTRQPHONIC FILTER Filed Nov. 18. 1951 2 Sheets-Sheet 2 Geo yea Mafiloux Arid/ 71e,

Patented Feb. 5, 1935 Y r 9 0 UNITED STATES PATENT OFFICE Georges Mabboux, Paris, France Application November 18, 1931, Serial No. 575,911 In Belgium November 26, 1930 12 Claims. (01. 1791) The present invention relates to elcctrophonic sented in Figures 1 to 3 and including a pluralfilters and, more particularly, to those of the ity of manual controls for instantaneously moditype adapted to be used for modifying the sound fying the action of the latter. emitted in assemblies employed for sound pic- Referring to Figure 1 of the drawings, there is 5 tures, radio telephony and the like. shown a Wheatstone bridge assembly in which 5 Electrical filters based upon the Wheatstone conductors a a receive current, while conductors bridge are already in -use wherein the various b b deliver current, or conversely. Conductor branches are provided with resistances or ima is provided with a sliding contact A capable of pedances, the latter being generally fixed. being displaced along a resistance (potentio- One of the objects of the invention is to prometric hook-up) so that p R of S d eS 10.

vide a slide-bridge type of Wheatstone filter in ance lies in branch 11 b and part It in branch which two branches of the bridge are provided il b. Branch b 11 is provided with an adwith a sliding contact which may be displaced justable capacity C while branch a, b includes along an impedance (ohmic resistance, selfinan adjustable self-inductance L 7 l5 ductive impedance or capacity) whose electrical When contact A is moved into position so that 15 properties may be distributed in accordance with the value of resistance R is approximately zero, any predetermined law, the other branches of the the filter has the characteristics ofa so-called bridge being provided with adjustable impedlow-pass type; hat is to ay. it permits the ances. passage of only low frequencies. If, on the other Another object is toprovide a Wheatstone ashand, contact A is displaced so as to render the 0 sembly of the type described in which impedvalue of resistance R nearly zero, the filter preances are connected to certain of the branches sents the characters of aso-called high-pass through the-intermediary of transformers whose type; that is to say, one, which permits the paseifect may be varied or whose coeflicient of transsage of only high frequencies. formation may be adjusted at will. I By adjusting the variable impedances of the 2 An add t o al object is to provide a Wheatfour branches of the slide bridge, it thus becomes stone assembly in which at least two of the possible to modify the characteristics of the filter branches are systematically .coupled so as to at will and prog ess ve y, if d d, the produce a variable effect or a change in translow-pa s to th hp yp as W as to formation ratio. vary the frequencies of resonance and to elimi- A further object is to provide a Wheatstone nate the desired frequencies. assembly of the type hereinabove described If it be desired to attenuate the effect of the wherein means are included for changing opervariation in impedance on theinput and outation instantaneously from any given intermediput circuits of the bridge as a function of the ate adjustment to certain extreme adjustments frequency, the latter may be provided (Figure 2) and inversely. with oscillation dampening impedances present- Another object still is to provide a stand or ing, preferably, characteristics which are the insimilar supporting, structure with handles, verse of those of the input and output circuits switches and the like, permitting a musician or and which can, under certain conditions, be reoperator to quickly and easily modify the action duced to simple resistances such as R or R posiof the filter so as to change the quality, volume, tioned across oneof the diagonals of the bridge, timbre, etc., of the sound being emitted continuresistance R being provided with some such adu y. I justing element as H.

Still further objects will appear in the course The form of assembly represented in Figure 3 of the detailed description now to be given with 'is similar to the one illustrated in Figure 2. 45

reference to the accompanying drawings, in However, it is to be noted that capacity C of ,which: branch N, a in the latter is replaced by a re- Figure 1 is a wiring diagram showing one ilsistance R or any other impedance (series, parallustrative embodiment of the invention; lel, or complex) while self-inductive impedance Figure 2 is a wiring diagram of a second pos- L of Figure 2 is replaced by a resistance R or sible embodiment; by any other form of impedance (series, parallel,

Figure 3 represents, diagrammatically, a third or complex). & form of the invention; In order to vary the selectivity of the electro- Figure 4 illustrates, in perspective, a stand phonic circuits, recourse may be had to adjustible 1 55 adapted to submit dructures of the type repredamping resistances connected, preferably, to at 7 5 is being shown may correct imperiections in reof resistances R or B. These damping resistances such as R" may be composed, at least in 'part, by a fraction taken from the charge impedance, for example, from R utilizing a potentiometric hook up provided with a sliding contact F.

The assembly may further be provided with impedances such as resistance R, a self-inductance or a condenser acting on said filter, for example, on impedance R through the intermediary of a transformer T fitted with a control D and of a variable coupling type or having a variable coefiicient of transformation.

A systematic coupling may further be introduced between any two branchesof the bridge (for example, between branches b a and b, a) through the intermediary of a transformer '1 fitted with a control E, the coupling being variable or having a variable coefiicient of transformation.

The assembly represented in Figure 3 is further provided with means for instantaneously passing from any position of intermediate adjustment to any one of the extreme conditions of low pass or high-pass operation. To this end, shunt circuits are separately. connected to resistances R and R and sliding contact A and a pair of switches are introduced into the two circuits in the manner shown-in Figlne 3. By reference to the drawings, it will at once be seen that, if control M connected to one of the switches is moved into contact with terminal and control N of the other switch into contact with terminal a, resistance R will be cut out of the circuit. Contrarywise, when elements M and'N are moved into contact with terminals :1: and resistance R will becut out. If elements M'and N are brought back into their intermediate positions as shown in Figure 3, the original state of operation between high and low-pass is reestablished.

In order to permit large scale manufacture of filters of the type described so that the latter maybe coupled to electrophonic circuits in current use having impedances of their own, transformers T and T of variable transforming ratio aremounted in the input and output circuits of the filter, the controls for varying the operating ratios of said transformers being arranged for separate or simultaneous adjustment. With these auxiliary structures the filter-is capable of operating without being eifected by the characteristics of the circuits to which it is coupled.

Figure 4 represents a filter and controls of the type shown in Figure 3 mounted for operation in assembledrelation on an operating support. Here, element 1 is a stand of the type commonly employed for orchestra leaders and is provided with a box 2 designed to receive any one of the types of filter shown in Figures 1 to 3. A series of control handles A, F, M and N and dials D and E traverse the walls of element 2 and have each a function corresponding to that of the elementsbearing the same reference characters inFigure 3. If desired, an oscillatable pedal H similar to'the pedals of expression used on organs may be added and may control the intensity of sound transmitted by varying damping impedance It. This pedal should be mounted so that it conserves any given position of adjustment when released.

With a stand of the-type described, a musician or operator seated in a hall in which a sound film vdecreasing another.

production in the course of the audition and may equalize the sonorous quality of successive sections of the film which as ordinarily produced frequently present considerable variations. It will be seen that the filter forming the subject matter of the present invention may be used to render reproduction homogeneous both as to timbre and intensity.

It is also obviousthat, by manipulating the various operating handles, any desired interpretation may be given to the music being reproduced in accordance with the taste, preference, or personal interpretation of the musician-operator. The musician maymoreover, render the sound being produced very shrill or very low so to accentuate sound effects produced by a drum or other instrument of percussion and modify the sound accompanying the explosion of a cannon or the whistle of the locomotive.

If it be desired to use the filter for recording a musical work, it should be intercalated in the circuit connecting the microphone to the recording apparatus. The correction of a first record-' ing operation may be effected by rerecording in a similar manner. The invention may be further applied to the control of the quality of radio emission, the musician following and correcting the latter-with a receiving apparatus while manipulating a filter connected either to the emitting of receiving stations.

What I claim is:

1. In combination with an electrophonic circuit, a filter including a Wheatstone bridge circuit, said bridge circuit comprising an input circuit and an output circuit, branches connecting each conductor of the input circuit with each conductor of the output circuit, an impedance in each branch, one pair of adjacent branches having their impedances serially connected to form a common impedance, and means for simultaneously distributing said common impedance between said pair of adjacent branches in varying proportions.

2. A structm'e as defined in claim I in combination with an impedance connected across a diagonal of said bridge circuit.

3. A structure as defined in claim 1 in combination with a variable impedance connected across a diagonal of said bridge circuit.

4. A structure as defined in claim 1 in combination with a variable resistance connected across a diagonal of said bridge circuit.

5. In combination with an electrophonic circuit, a filter including a Wheatstone bridge, said bridge having a variable capacity inserted in one branch thereof, a variable self inductance inserted in a second branch thereof, a pair of branches '7. In combination with an cuit, a filter including a Wheatstone bridge circuit, said bridge circuit comprising an input circult and an output circuit, branches connecting each conductor of the input circuit with each conelectrophonic cirductor oi the output circuit, a variable impedance in each branch, an impedance inserted diagonally across said bridge circuit, and means connected to one of said branches for exerting a damping eflect.

8. In combination with. an electrophonic circuit, a filter including a Wheatstone bridge, said bridge having branches provided with variable impedances and also having .an impedance inserted diagonally thereacross, said bridge further having potentiometric means extending from one branch thereof to the diagonal impedance.

9. In combination -'with an electrophonic circuit, a filter including a Wheatstone bridge, said bridge including an impedance distributable between a pair of adjoining branches, means for distributing said impedance in varying proportions between said branches, and switch means operative to cut out the impedance forming part of either one of said branches.

10, In combination with an electrophonic circuit, a filter including a Wheatstone bridge circuit, said bridge circuit comprising an input circuit and an output circuit, branches connecting each conductor of the input circuit with each conductor oi! the output circuit, a slide wire serially connecting one pair of adjacent branches, an impedance in each of the other branches'ot said bridge circuit, and means associated with saidslide wire to distribute resistance between said pair 01' adjacent branches.

11. In combination with an electrophonic cir- '.cuit, a filter including a Wheatstone bridge circuit, said bridge circuit comprising an input circuit and an output circuit, branches connecting each conductor of the input circuit with each conductor of the output circuit, an impedance in each branch, means .ior inductively and adjustably coupling the impedance in one branch with the impedance in another branch.

12. In combination with an electrophonic circuit, a filter including a Wheatstone bridge circuit, said bridge circuit comprising an input circuit and an output circuit, branches connecting each conductor 01 the input circuit with each conductor of the output circuit, a resistance inserted in one of the branches of said bridge, an'

impedance in another branch, means for inductively and adiustably coupling said impedance with said resistance, and impedances in said other branches.

' GEORGES MABBOUX. 

